From watching actual decent mechanics on YouTube that doesn’t always hold true. Seems some people’s dislike of having emissions control leads them to believe it can be the only option if something goes wrong that might be linked. Seen several vehicles now come into these garages with the client saying ‘last garage did x,y or z’ to the DPF/EGR system etc, the problem isn’t fixed, and they don’t know what else it can be’.but people rarely tamper with stuff if it's not causing some sort of problem.
Not saying it can’t be the problem or doesn’t sometimes cause issues, especially when servicing is inadequate or the vehicle only sees short journeys, but people jump to that conclusion too quickly now.